How do moose communicate in the woods?

I remember a time when my father took me out hiking. We took a trail along the Campbell Creek near the airstrip. It was in the middle of town, but it sure seemed a lot farther out. We had hiked for about four hours along the trails when we stopped for lunch. We sat down in a clearing next to the trail; I began to remove my backpack when my dad held up his hand. It was a signal for me to stop and listen. I didn’t hear anything, but dad said that we needed to find someplace else to eat. The clearing wouldn’t be safe much longer. I was hungry, but I knew better than to talk back to my dad. I put the backpack back in place, and we continued on. On the trail further down, dad put his hand up again, “Do you hear that, son?” I shook my head. I didn’t hear anything but the normal sounds of the wilds of Alaska. “Listen carefully. Thump. Thump. Thump. Scratch. Thump.” With dad’s vocal emphasis on the background noises, I did begin to hear it. “What is it, dad?” Dad held his hand up again and listened. After a little bit he said, “A bear is following us. Apparently, we aren’t making enough noise to convince we aren’t food.” I looked around. I knew we were far from the car and that bear attacks had occurred in the area. “How do you know? I don’t see any bear.” I shouted hoping it would scare the predator away. “I know it from the thumping and scratching you heard.” “What?” I was still yelling. “How did you get anything from that?” “Son, your grandfather was a wise person. One of the first things he taught his children was how to listen to the wilderness. Among his lessons was how moose survive. They have to worry about men and wolves and bears, so they have a pretty good communication system for locating and avoiding predators.” “Really?” I was still looking for the bear. “And your granddad made sure that we all learned the way the moose communicate. He called it Moose Code.”